The present invention was conceived in the context of on-board central tyre inflation systems (CTISs) for land based vehicles. CTISs were originally developed for military applications, in particular for military applications concerning off-road military wheeled trucks and trailers. However, CTISs are nowadays incorporated into non-military vehicles such as specialist construction equipment and some agricultural vehicles.
A CTIS typically comprises one or more compressed air sources located on-board the vehicle and connected to one or more tyres. Tyre pressure can therefore be adjusted by operating the CTIS. Typically, a CTIS provides for delivery of compressed air to a tyre supply line. In some examples, the supply line is integrated into a vehicle axle. Some axles comprise articulated joints having a driveshaft and a stub axle connected to form a constant velocity (CV) joint, and the compressed air supply line extends through the CV joint. The CV joint is typically protected by a CV joint gaiter. An example of such an axle is described in US 2012/0067482 A1, to Mr Clyde Stech of Fleet Air, LLC.
Air supplied through the CV joint to inflate or deflate the tyre may leak into the CV joint enclosure delimited by the gaiter and thus inflate the gaiter. This is not desirable, and vented gaiters have been proposed to equalise pressure. However, vented gaiters need to be kept unobstructed to vent air efficiently. The present invention seeks to provide an alternative solution to vented gaiters.
U.S. Pat. No. 8,075,669 B2 discloses a gas-permeable oleophobic material.
EP 2,007,500 B1 discloses a vent for an enclosure containing lubricated machinery.
WL Gore & Associates, Inc., supplies the series AVS 41 automotive vents for powertrain components. An AVS 41 vent comprises a body, a membrane, a pre-filter and a cap. When the vent is installed in a venting opening, air is vented in sequence through a conduit, through the pre-filter and through the membrane. The membrane is located after the pre-filter with respect to the venting direction.
It is against this background that the present invention has been conceived. In at least certain embodiments, the present invention seeks to address shortcomings associated with the prior art or to improve parts, components, apparatus, systems and methods disclosed in the prior art.